In situ construction of hierarchical core-shell SiC_nws@SiO₂-carbon foam hybrid composites with enhanced polarization loss for highly efficient electromagnetic wave absorption

The drawbacks of single loss capability and skin effect severely impede the electromagnetic (EM) wave absorption performance of carbon-based materials. Developing a rational hierarchical structure with high efficiency and facile method to optimize impedance matching and improve EM wave absorption performance still remains challenge. Herein, SiC_nws/carbon foam (SCF) composites with hierarchical structure, were successfully prepared by chemical vapor deposition method. The core shell structure of SiC_nws@SiO₂ was grown on the scaffold and inside of the cell structure in CFs. Significantly, the amount of SiC_nws can be modulated by the growth temperature. Benefiting from the impedance gradient structure, coupled with interface polarization dominated loss mechanism jointly promoted the excellent EM wave absorption performance. Specifically, when the growth temperature is 1400 °C, the SCF composite achieved an optimal reflection loss value of −55.8 dB at 10.30 GHz with a thickness of 4.35 mm and a wide effective absorption bandwidth of 3.97 GHz at 3.71 mm. Meanwhile, in-situ growth of SiC_nws in CFs substantially increased the compressive strength to 21.08 MPa. This work paves a new avenue to develop highly efficient EM wave absorption materials with hierarchical structures.